Black holes and the relativity of simultaneity

[RJBeery]

(Also posted this at Physicsforums.com but I don't think that's against the rules)

Over the years I've watched Science try to deal with the Information Paradox regarding black holes.

http://news.sciencemag.org/physics/2015/12/physicists-figure-out-how-retrieve-information-black-hole

I've always been curious how we got to the point where we see this as a problem in need of a solution. In order for information to be "in" a black hole, and theoretically unavailable to us, it must have crossed the event horizon from our perspective, correct?

We talk about the existence of black holes as a matter of fact, in present tense, but present tense existence of spatially distant objects (i.e. events) are space-like separated by any definition, and I don't think anyone will disagree with this. The temporal order of space-like separated events is ambiguous, and can be changed based on the frame of the observer. Now, follow this logic:

Let's denote an event a "growth event" when matter crosses an event horizon. In order for a black hole to presently exist with a non-zero radius for an observer, that observer must have "growth events" in his or her past light cone. The claim that a black hole currently exists for us fails on two counts: firstly because no such black hole growth events have occurred in any of our past light cones and, secondly, because there are no frames which can claim otherwise for us or themselves.

The typical response to this point is frame jumping by imagining ship A free-falling across an event horizon E with sufficiently low (survivable) tidal forces; however, this requires the existence of a black hole in the first place! We cannot use an imaginary black hole to prove the existence of theoretical black holes unless we are able to provide a theory of how they came to be in the first place. The problems faced by us on Earth would also exist for ship A; the existence of E could not be explained by any events in A's past light cone.

At this point, Kruskal (or some other) coordinates are dragged out. Again, there is no point to this. Kruskal coordinates are only needed to analyze anexisting black hole, and are not needed to discuss the birth of one. Additionally, no valid coordinate system (including Kruskal) can put growth events into the past light cone of any observer.

I don't mean to have a contentious tone, but I am frustrated by my inability to find someone who can convince me that black holes aren't a grand example of the Emperor having no clothes.

Oh, and MERRY CHRISTMAS!

 

[brucep]

(Also posted this at Physicsforums.com but I don't think that's against the rules)

Over the years I've watched Science try to deal with the Information Paradox regarding black holes.

http://news.sciencemag.org/physics/2015/12/physicists-figure-out-how-retrieve-information-black-hole

I've always been curious how we got to the point where we see this as a problem in need of a solution. In order for information to be "in" a black hole, and theoretically unavailable to us, it must have crossed the event horizon from our perspective, correct?

We talk about the existence of black holes as a matter of fact, in present tense, but present tense existence of spatially distant objects (i.e. events) are space-like separated by any definition, and I don't think anyone will disagree with this. The temporal order of space-like separated events is ambiguous, and can be changed based on the frame of the observer. Now, follow this logic:

Let's denote an event a "growth event" when matter crosses an event horizon. In order for a black hole to presently exist with a non-zero radius for an observer, that observer must have "growth events" in his or her past light cone. The claim that a black hole currently exists for us fails on two counts: firstly because no such black hole growth events have occurred in any of our past light cones and, secondly, because there are no frames which can claim otherwise for us or themselves.

The typical response to this point is frame jumping by imagining ship A free-falling across an event horizon E with sufficiently low (survivable) tidal forces; however, this requires the existence of a black hole in the first place! We cannot use an imaginary black hole to prove the existence of theoretical black holes unless we are able to provide a theory of how they came to be in the first place. The problems faced by us on Earth would also exist for ship A; the existence of E could not be explained by any events in A's past light cone.

At this point, Kruskal (or some other) coordinates are dragged out. Again, there is no point to this. Kruskal coordinates are only needed to analyze anexisting black hole, and are not needed to discuss the birth of one. Additionally, no valid coordinate system (including Kruskal) can put growth events into the past light cone of any observer.

I don't mean to have a contentious tone, but I am frustrated by my inability to find someone who can convince me that black holes aren't a grand example of the Emperor having no clothes.

Oh, and MERRY CHRISTMAS!

No wonder you can't figure it out. You still can't figure what the coordinates mean. Seems like myself and others have explained this to you. You're not really interested in the physics beyond you being right. That's my conclusion from all the irrelevant nonsense you've posted on this subject.LOL. Back again.
*plonk*

 

[RJBeery]

No wonder you can't figure it out. You still can't figure what the coordinates mean. Seems like myself and others have explained this to you. You're not really interested in the physics beyond you being right. That's my conclusion from all the irrelevant nonsense you've posted on this subject.LOL. Back again.
*plonk*

I'm not interested in being right, I'm interested in being given a reasonable explanation on why I'm wrong. If you believe you've done this in the past please reiterate your position or provide a link. It's OK not to have an explanation, but please don't clutter the thread with posts void of content.

 

[brucep]

No wonder you can't figure it out. You still can't figure what the coordinates mean. Seems like myself and others have explained this to you. You're not really interested in the physics beyond you being right. That's my conclusion from all the irrelevant nonsense you've posted on this subject.LOL. Back again.
*plonk*

When Penrose and Hawking, and other contributors, solved the singularity theorem they used local proper coordinates where all geodesic terminate at r=0. For this analysis they need local proper coordinates. IE
https://en.m.wikipedia.org/wiki/Gravitational_singularity

 

[RJBeery]

When Penrose and Hawking, and other contributors, solved the singularity theorem they used local proper coordinates where all geodesic terminate at r=0. For this analysis they need local proper coordinates. IE
https://en.m.wikipedia.org/wiki/Gravitational_singularity

I'm not refuting any mathematical analysis of the mathematical object that is a black hole. I'm questioning the physicality of it for the reasons listed in my OP.

 

[DaveC426913]

I'm not sure what you're saying. Are you saying that it is impossible for a black hole to form in the first place, perhaps because infalling objects never appear to cross the horizon?
Am I close?

 

[brucep]

I'm not sure what you're saying. Are you saying that it is impossible for a black hole to form in the first place, perhaps because infalling objects never appear to cross the horizon?
Am I close?

Yes that's what he's saying. In the process he's claiming the real physics is conducted from remote coordinates. That remote coordinates are preferred over local proper coordinates. That' a clueless claim from a clueless crank. Get ready for the big obfuscation.

 

[Schmelzer]

Coordinates are quite arbitrary, in the GR spacetime interpretation they play no fundamental role, but are not more than coordinates. Global coordinates should not even exist (they cannot if the topology is nontrivial). No global timelike coordinate is obliged to exist - in solutions like the Gödel universe, which have closed causal loops, none exists. If they exist, they mean nothing: There are time coordinates for black hole collapse where the black hole horizon is never formed, and others where it forms a short time after the gravitational collapse starts.

If one does not like this, and finds that, for whatever reason, a global time coordinate exists, even if we cannot measure it, we have to modify the spacetime interpretation. We have to throw away wormholes and other solutions which do not allow for global coordinates, we have to throw away solutions with close causal loops, and all this is not yet enough, because if this global time exists, unmeasurable or not, it should have a physical equation. Fortunately, there are not many equations to choose between, the only plausible candidate is the harmonic equation for the time coordinate. But this harmonic time coordinate, with Minkowski time initially before the collapse, gives a global time coordinate which excludes the part behind the horizon, so that no horizon is formed.

 

[krash661]

I'm not interested in being right, I'm interested in being given a reasonable explanation on why I'm wrong. If you believe you've done this in the past please reiterate your position or provide a link. It's OK not to have an explanation, but please don't clutter the thread with posts void of content. [...] I'm interested in being given a reasonable explanation on why I'm wrong.

what if no one cares for what you cannot comprehend while you continue to(for years now) insult science/scientist-- only, simply, from a result of you thinking you are some kind of intellect/genius?

If you believe you've done this in the past please reiterate your position or provide a link. It's OK not to have an explanation, but please don't clutter the thread with posts void of content.

this is obviously a pathetic, primitive, tactic-- you well know that this has occurred many times over the years(with your continuous, repetitious --same ole'-same ole' topics). why are you initiating these pathetic shenanigans?

 

[brucep]

Coordinates are quite arbitrary, in the GR spacetime interpretation they play no fundamental role, but are not more than coordinates. Global coordinates should not even exist (they cannot if the topology is nontrivial). No global timelike coordinate is obliged to exist - in solutions like the Gödel universe, which have closed causal loops, none exists. If they exist, they mean nothing: There are time coordinates for black hole collapse where the black hole horizon is never formed, and others where it forms a short time after the gravitational collapse starts.

If one does not like this, and finds that, for whatever reason, a global time coordinate exists, even if we cannot measure it, we have to modify the spacetime interpretation. We have to throw away wormholes and other solutions which do not allow for global coordinates, we have to throw away solutions with close causal loops, and all this is not yet enough, because if this global time exists, unmeasurable or not, it should have a physical equation. Fortunately, there are not many equations to choose between, the only plausible candidate is the harmonic equation for the time coordinate. But this harmonic time coordinate, with Minkowski time initially before the collapse, gives a global time coordinate which excludes the part behind the horizon, so that no horizon is formed.

The coordinates are solutions to field equations. The one he's saying is preferred over all others is Schwarzscild bookkeeper coordinates. GR is a frame independent local theory of gravity. Also included is coordinate solutions which are really good for analyzing the spacetime. For this case he thinks the only valid solution is the Schwarzschild remote bookkeeper solution.

 

[Schmelzer]

The coordinates are solutions to field equations.

???? Not in GR with Minkowski spacetime interpretation. There you can use arbitrary coordinates x'(x) and transform any solution in any other coordinates x into a solution in new coordinates x'. The only thing which is fixed are rules to transform a solution in one set of coordinates into a solution in any other set. The coordinates may by arbitrary (ok, they have to be smooth, but that's all).

 

[RJBeery]

???? Not in GR with Minkowski spacetime interpretation. There you can use arbitrary coordinates x'(x) and transform any solution in any other coordinates x into a solution in new coordinates x'. The only thing which is fixed are rules to transform a solution in one set of coordinates into a solution in any other set. The coordinates may by arbitrary (ok, they have to be smooth, but that's all).

Schmelzer, I appreciate that coordinates are arbitrary and I'm not assigning a frame or a coordinate system as "preferred". I'm pointing out that in order for an observer, who is external to a black hole, to claim that the black hole exists with a Schwarzschild radius > 0, there must be a "birth event" and subsequent "growth events" identifiable in his past light cone. This is incontrovertible. Valid coordinate transformations cannot violate causality.

Discussing Godel's closed causal loops, worm holes, etc, is fine, but examine your logic closely:

Global coordinates should not even exist (they cannot if the topology is nontrivial)...We have to throw away wormholes and other solutions which do not allow for global coordinates, we have to throw away solutions with close causal loops, and all this is not yet enough, because if this global time exists, unmeasurable or not, it should have a physical equation

I'm asking for a rigorous definition of "existence" that can justify black holes for any observer, anywhere, at any time in the past or finite future. Part of your apparent defense of black holes is that they are allowed if we are to accept other non-trivial topologies (whose existence would necessarily be brought into question). I have no motivation to accept non-trivial topologies as existing without a rigorous definition of "existence", do you? You are defending one theoretical mathematical object with others whose definitions suffer the same shortcoming. Pointing out that "existence" has no concrete meaning in a Universe with non-trivial topology is a circular argument and presupposes the latter without justification. Attempting to invalidate the definition of "existence" does cannot prove the existence of something, so this really doesn't get us anywhere.

 

[DaveC426913]

Well, black hole are not theoretical. We've observed them.

You're going to have to approach this from the top down. Theses are observations we have - now what kind of object could possibly produce the phenomena we are witnessing?

Were you to disprove our current understanding of the existence of black holes, you'd still be left with objects we've seen that require explaining.

 

[RJBeery]

Well, black hole are not theoretical. We've observed them.

You're going to have to approach this from the top down. Theses are observations we have - now what kind of object could possibly produce the phenomena we are witnessing?

Were you to disprove our current understanding of the existence of black holes, you'd still be left with objects we've seen that require explaining.

This is true but current theory already accounts for that. Black hole "regions in space" are simply dark areas, just as we would expect to see from asymptotic red-shifting as the neutron star approaches (but never quite collapses beyond) the Schwarzschild radius. Our mathematical treatment of the event horizon would simply apply to the center of mass of the object.

 

[DaveC426913]

This is true but current theory already accounts for that. Black hole "regions in space" are simply dark areas, just as we would expect to see from asymptotic red-shifting as the neutron star approaches (but never quite collapses beyond) the Schwarzschild radius. Our mathematical treatment of the event horizon would simply apply to the center of mass of the object.

Except that the gravity generated by that mass is greater than that required to overcome neutron repulsion. Our physics says it cannot be a neutron star. It does collapse to something smaller, we just don't know what. Whatever that is, we call it a black hole.

 

[paddoboy]

I'm asking for a rigorous definition of "existence" that can justify black holes for any observer, anywhere, at any time in the past or finite future.

It appears all you are doing is questioning the fact that all Frames of references are as valid as each other.
Reminds me of the Mars Curiosity Rover and its descent and landing on Mars.
When mission control received the precise data that the Rover had disengaged from the orbiter, before its perilous journey through the atmosphere and its "never before attempted landing methodology"on the red planet, curiosity was already on the surface and was beginning its exploration mission of Mars.
Simply put, there is no universal now due to the fact of the finite speed of light and time dilation.
So, yes, most certainly BH's do exist, and just as certainly, we will never see any object cross the EH, for the reasons stated.
Unless of course you have another valid explanation to explain the effects we see on matter/energy and spacetime surrounding such objects.
And just as certainly any explanation would be just as bizarre as the accepted BH explanation.

 

[paddoboy]

Except that the gravity generated by that mass is greater than that required to overcome neutron repulsion. Our physics says it cannot be a neutron star. It does collapse to something smaller, we just don't know what. Whatever that is, we call it a black hole.

Yes, I thought that would have been obvious to someone trying to question the validity or otherwise of a BH.

 

[paddoboy]

This is true but current theory already accounts for that. Black hole "regions in space" are simply dark areas, just as we would expect to see from asymptotic red-shifting as the neutron star approaches (but never quite collapses beyond) the Schwarzschild radius. Our mathematical treatment of the event horizon would simply apply to the center of mass of the object.

http://www.deepastronomy.com/how-do-we-know-black-holes-exist.html

One of these sources however, a source known as Cygnus X1, did not fall into this category.

Neutron stars are formed from the collapse of stars less than three times the mass of the Sun. From uhuru data, The companion to this star appeared to be five to eight times the mass of the Sun, this object was too large to be a neutron star. Current, more recent estimates put the mass of this companion at least 10 solar masses.

This could be nothing other than a black hole.

After hundreds of years of theory and speculation, black holes have moved into the realm of observation. Their discovery was as unexpected as it was strange. Luckily for us, the truth of the universe isn't limited by our feeble ability to understand it.

 

[paddoboy]

http://arxiv.org/abs/1503.03873

The Event Horizon of M87

ABSTRACT:

The 6 billion solar mass supermassive black hole at the center of the giant elliptical galaxy M87 powers a relativistic jet. Observations at millimeter wavelengths with the Event Horizon Telescope have localized the emission from the base of this jet to angular scales comparable to the putative black hole horizon. The jet might be powered directly by an accretion disk or by electromagnetic extraction of the rotational energy of the black hole. However, even the latter mechanism requires a confining thick accretion disk to maintain the required magnetic flux near the black hole. Therefore, regardless of the jet mechanism, the observed jet power in M87 implies a certain minimum mass accretion rate. If the central compact object in M87 were not a black hole but had a surface, this accretion would result in considerable thermal near-infrared and optical emission from the surface. Current flux limits on the nucleus of M87 strongly constrain any such surface emission. This rules out the presence of a surface and thereby provides indirect evidence for an event horizon.

 

[paddoboy]

https://briankoberlein.com/2015/08/16/do-black-holes-really-exist/

There are basically two lines of evidence to support the existence of black holes. The first is observational. For small (stellar mass) black holes, the best evidence is through micro-quasars, also known as x-ray binaries. These objects emit strong x-rays from an Earth-sized region in space. Since these objects are part of a binary system with another star, we can determine their mass by the way the two stars orbit each other. What we find is these dense objects have masses that range from 1 – 10 times the mass of our Sun.


An example of differential rotation.

Stellar mass black holes are expected to emit strong x-rays when material near the black hole gets super heated due to all the gravitational compression. So this is exactly what we expect from a black hole. The problem is that neutron stars can also emit strong x-rays because they also have strong gravitational and magnetic fields. But it turns out that neutron stars, like our Sun undergo an effect known as differential rotation. Instead of rotating like a solid object, the equator region of a neutron star makes a complete rotation in less time than their polar regions. As a result their magnetic fields get twisted up until they snap back into alignment. For the Sun differential rotation leads to things like sunspots and solar flares. A similar effect occurs for neutron stars. As a result, some x-ray binaries are known to have differential rotation, and there therefore neutron stars. Other x-ray binaries don’t undergo differential rotation, so they are known as black hole candidates (BHCs).

We have similar observational evidence for supermassive black holes. For example, we know that quasars can emit more light than 250 billion stars from a region no larger than a light year across. When we observe the motions of stars near the centers of galaxies, they reveal thepresence of a dense mass on the order of millions or billions of solar masses. In some cases we can even determine the mass of these central objects with great precision. But some of the strongest evidence comes from our own galaxy. With modern telescopes we’re able to image stars in the center of our galaxy. Over the years we’ve watched these stars as they clearly orbit a large dense mass. We know that this object has a mass of 4.1 million solar masses, and that all this mass can be no larger than our solar system (about 100 astronomical units across to be precise).

The other line of evidence is theoretical, specifically the theory of general relativity. Einstein’s theory of gravity makes very clear predictions about the motions of planets, how light is affected by gravity, gravitational redshift, the timing of GPS, and even thetwisting of space and time. Every experimental test we’ve tried so far, general relativity has passed.